Unidirectional current-carrying device



Aug. 23, 1927. L

o. GRONDAHL V UNIDIRECTIONAL CURRENT CARRYING DEVICE Filed Jan. 7, 1925 l2 sheets-sheer 1 INVENT'oR @ra-@Mug L. O. GRONDAHL UNIDIRECTIONAL CURRENT CARRYING DEVICE Aug. 23 1927'.

Filed Jan.v v. 1925 2 sheets-sheer 2 Fig. 10.

INVENTOR Maan-73 Patented lAug. v23, 11927.

UNlTE-D STATES- PATENT OFFICE.

LABS 0. GRONIDAHL,V OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION 0F PENNSYLVANIA.

'UNIDIRECTIONAL CURRENT-CARRYING DEVICE.

Application lcld January My invention relates to luni-directional current carrying devices, that is, devices.

- to the two is concerned.

- claims.

ln the accompanying drawing, Fig. l is a sectional view showing one form of device embodying my invention. Fig.' 2 is a view showing a modification of the device shown in Fig, l. Fig. 3 is a view showing a device made up of three units each similar to the device shown in Fig. l. Figs. 4 and 5 are views showing other inoditications of the device shown in Fig-l, and also embodying my invention. Fig. 6 is a diagrammatic view showing a current carrying device embodyingmy invention associated with a storage battery in such manner that the battery may be charged from'a source of alternating current. Fig. 7 is a longitudinal sectional view showing a modified form `of device embodying my invention arranged to utilize both halves of each wave of an alternating current. Fig. 8 is an end view of the device illustrated in Fig. 'i'. Fig. 9 is a diagrammatic view showing one arrangement of electricall circuits and apparatus including the device illustrated in Figs. 7 and 8. Fig. 10 is a sectional view showing a modified form of device embodying my linvention adapted to transmit current of comparatively large value.

Similar reference characters refer to simi- .lar parts in each of the several views.

Referring first to Fig. l, the device or unit,

which is designated as a whole by the refer-l ence character A, comprises a metal plate or electrode 10, and a compound 10a in intimate' electrical-contact with a surface of the plate. The compound 10 is preferably a compound of the metal which constitutes the plate, and it is preferably formed directly on .the plate.

7, 1925. semi no.' 1,111.

per, and the compound 10., which may be termed the surface coating, may` be cuprous oxide. As another example, the metal plate 10 may be iron, and the compound or surface coating 10 maythen be an iron oxide. Against the layer of oxide 10a is placed a second electrodecomprising one or more sheets 1l of a conductor of a'soft, impressionable character such, for example, as lead foil, and

next to the foil 11 is another plate l2 of conductive material, such as copper. The elements'of the device are pressed tovether by means not shown in this view, and the two outside metal plates 10 and l2 are used as vterminals for passing electric current through the device; for this purpose terminal conductors 13 and la may be provided,

if desired.

l" have found that a device constructed.l in the manner just described has a lower resistance when current passes from the compound l0a to the metal plate 10 than when current passes in the opposite direction, and, consequently, the device may be termed a uni-di` rectional current carrying device, or a rectilier. By thisxpression l do not mean that no current will pass through the device in one direction, but only that the conductivity 1n one direction is considerably greater than in the other direction. This property maires it possible to use the device as rectifier,

that is, as a device for transforming alternating current into a substantially uni-directional current.

ln the practice of my invention, It preferably forni the oxide directly on the metal by oxidizing the niet-al at a relatively hi temperature in an atmosphere containing oxygen. n ln the case of copper, the tempera-- ture used should he inthe neighborhood ot 1000o C., and below the melting pointl of copper, such a temperature apparently being essential to the :formation of a compound having the proper homogeneity, that is, nonporosity. ln preparing this oxide there is always formed a very thin layer of cupricoxide on the surface of the cuprous oxide which constitutes the main body of the oxide. This layer of cupric oxide is preferably removed by suitable means, such, for example, as emery cloth, or a sand blast, or

vnitric, acid, although the removal of such layer is not essential. The device without As an example, the plate 10v may be of copthe cupric oxide removed will function as a Uli rectifier, but rectification is believed to be due solely to the combination of cuprous oxide and copper in intimate contact, and the cupric oxide is preferably removed to reduce the resistance of the device.

lu the case ofthe copper-caprous oxide rectifier, Vformation of the cu rous oxide directly on the copper by oxi ation seems to he essential to attainment of the desired characteristics.

In order to assure good results, the surface of the copper which is to carry the cuprous oxide should be smoot-h and clean. Some sheet copper hasthe appearance of having wrinkled on one side while cooling; such sheets will produce a good rectifier when the smooth side is used to carry the oxide, and a poor rectifier when the wrinkled side is so used. I have not found that it makes yany difference whether the copper is hard or soft.

The compound which is formed on the metal must have substantially the same coefficient of expansion as the metal on which it is formed, or at least must adhere sufficiently well and be of such mechanical strength that it does not break loose from the metal on cooling. Perhaps the most essential characteristlc of the compound is that it must conduct electricity without decompositionor chemical change` that is. it must be stable or permanent. To give. this result the compound must be a metallic conduetor as distinguished from an electrolytic conductor wherein the com ound decomposes due to the flow of e ectric current through it. That is, `the compound must conduct current electronically and not ionically, and must remain` an electronic conductor under all reasonable operating temperatures. In the case of cuprous oxide, I have found no trace of counter electrometive force due to polarization, and no other signs of l decomposition after long use.

' Polarization would be ex ,ected if the compound were an electrolytic conductor.

Rectifiers embodying.. my invention have certain features or characteristics, some of which I will nowexplain.

Rectifyng ratto- The rectifier` offers "a relativel low resistance to current flowing in one dlrection, and a relativelyA high resistance to current flowing in the other direction. 4The ratio of the high resistance to the low resistance is conveniently termed the rectifying ratio of the device. The resist-l ances in the low and high resistance direc-t tions, and the rectifying ratio, vary in response to variation of several factors, some of which are as follows.

Variation of pressure- Within certain' limits, I have found that an increase of pressure causes an increase of the rectificationratio. In the case of one particular coppercuprous oxide specimen, a change from presby -a greater percentage than does the high reslstance. lIn the case of the specimen just referred to, the high resistance decreased from 620 ohms to 380 ohms as the pressurel increases from to 19.0 pounds per square inch, this change of resistance being about 39%; whereas with the same increase'of pressure the lowv resistance decreases from 22.5 ohms to 8.8 ohms, this change being about 83%. In the case. of the low resistance, the change is probably due largely to a decrease in the resistance of thecontact between the copper oxide and the second electrode 11 with increase of pressure.

Thickness of compound-As far as I have been able todetermine up to the present` time. the resistance constants of the device do not change materially `w1thchanges in the thickness of the compound. This woulda indicate that the p resistance constants 'primarily depend on the nature of the layer at the junction between the metal and the compound, and probably on the closeness ofthe relations between the same.

Ver-ation of eOZta/ga-In the case of one copper-cuprous oxide rectifier constructed in accordance with my invention, the resistance in the low resistance direction decreased rapidly from about 500 ohms at thelowest readable voltage to about ohms at 0.4 volt, and then decreased slowly to about 15 ohms at 8 volts. In the high resistance direction the resistance increased from about 500 ohms at the lowest readable voltage to about 1100 ohms at 1.4 volts, and then decreased to about 910 ohms at 8 volts.

@uwen-t carry/ng capacity/. -The amount of current that can be carried by the rectifier depends on the provision for carrying away the heat that is developed in the rectifier. The rectifier must be kept reasonably cool, as otherwise it. deteriorates due to thermal expansion, and in extreme cases it may melt the lead foil which is used for contact. The rectifier should, therefore, be operated at a fairly low temperatura-fand this can be accomplished by providing necessary ventilation; The only limit to the current carrying capacity that has thus far been found is the necessity for keeping the temperature low.

Pewnanenc3/.-Rectifiers embodying;d my invention deteriorate very slowly and 'very gradually, if at all. Y They do not deteriorate at all if they are properly constructed; that is, if they are clamped tightly and perma-A,

nently, and'if they are protected from chemical action dueto the constituents of the atmosphere.

ltlt) IZll . electronic valve which 'is encased by autres Ti/md lag.-Rectifiers embodying my invention are immediately operative in their stead condition the instant they are subjectet to voltage. By this' I ynienn that 'no period of time is required for the resistance actors to reach steady values. The` only change that will occur after the application of vo tage isa change in the resista-nce factors if' the current value is'sutiicient to cause a rise of temperature, and the time involved in this change is rather great, being usually of the order of several minutes. i

One important feature. ofmy invention is that the iectifiers, being electronic in nature,

. do notrequire forming, as do rectifiers of the electrolytic type such as4 those using aluminum and aluminum oxide. v

At the present time I believe that the main advantage of the `metal foil electrode 11 is that it provides a good electrical contact between the oxide 10 and the electrode 12. Perhaps this contact may be secured b other means, such for example, as a metal. li m deposited on the oxide b sputtering or electro-plating, and in fact t is second electrede may be anything which makes a good electrical contact with the cuprous oxide.' I have found it advantageous to rub tinely. divided carbon into the outer surface of the uprous' oxide before applying the metal It will be seen from `the foregoing that in my rectifier two lai-laterally conducting bodies are permanently joined to each other over a relatively extended area, and co-act with each other to produce in and by themselves a uni-laterally conducting combination. In this combination,the layer at the junction of the two bodies appears to constitute a permanent set-up of particles permitting a relatively free dow of electrons in the direction from the copper to the cuprous oxide, while obstructing the flow of electrons in the opposite direction. The rectifying action so obtained takes place without any observable physical or chemical changes in the bodies. yIn other woiids, the device can probably be described as a minue t e bodies on both sides 'of the rectifying yer, thus rotecting the rectification against ex ternadsturbing inuences.

Referring now to.. Fig. 2, the rectifier heresho'wn'is the .game as that illustrated in Fig.` l, except that the lead foil 11 is in sections so that it covers portions of the oxide 10, leaving the remaining portions exposed. This arrangement 'provides' for ventilation.

-two outer electrodes 12 whic the oxide.

over a suflicient number of sur aces4 to prevent undue rise4 in tem erature. f

Referring now t'b Fig. 4, the metal meml` b er 10 on which'v the oxide is formed, is in the shape ofa wire or rod, the entire c -A llndrical surface being provided with o xi e -10. Several. layers of lead foil 11 are Wrapped vvaround the oxide, and the outer electrode or terminal is .Wire 12 of co per or other suitable material wrapped tig tly around the foil.

In the arrangement shown in Fig. 5, both surfaces of the metal plate 10 are provided with oxide 10", and one or more sheets of lead foil 11 are laced in' contact with each layer cf oxide. he deviceis rovided with are electrically connected by a conductor 16 to form one terminal of the device, the other terminal being the inner plate 10. This structure permits the use of oxide on both sides of the metal member 10, and is advanta eous whenl the device comprises one unit on y.

Devices embodyin my invention may be used whenever it is desirable to supply uni directional current of substantial amount to a current consuming device froman ,alter- For example, they may be used as rectifiers for charging nating current source.

storage batteries from alternating current sources. When so used,`the arrangement of connections shown in Fi 6 may conveniently be employed; In tris view, B desig nates the battery, which is provided with terminals`17 and 18, Whereas the rectifier is desi nated R and may comprise lone or more of t e units shownin any of the preceding views. `One terminal of the rectifier is connected with battery terminal 18, and the revice embodying my invention is illustrated t in Figs. 7 and 8, in which views the reference character20 designates a long bolt rovided with a nu't 20, Mounted on the olt 20 are a plurality of uni-directional conducting units ach similar to the unit A of Fig. 1 in that it comprises a metal washer 10 havingan oxidized surface 10", and one or more sheets of lead foil 1l in contact with Each two adjacent unitsl are separated by a washer 1.2b of conducting material, such as aluminum or iron, which izo.

las

lll

y of the alternatingv current.

yan alternatin y 4battery in suc manner as to utilize both-the tral section by terminal plates 22 and 22,

respectively. The' units in the central Section C are all arranged for hi h conductivity from 'right to left, while t e units in the outer sections are arranged for high conductivity from left to right., these directions of high conductivit being indicated bythe arrows in Fig. 7 y virtue of this arran' ement, the rectifier may be connected wlth current source and a storage positive, and negative halves of each cycle To accomplish this, one terminal of an alternating current, such as the secondary of a transformer F is connected with the electrode 10 of the middle unit of section C by a wire 24, and the other termina-lof this source is connected -with bolt by a.wire 25. This bolt is in electrical contact with the left-hand 'unit of section D'through the medium of a washer 26, and with the right-hand unit of section E through the medium of a washer 27, so that the wire is in eii'ect electrically connected with these two outer units. The battery B is connected with the two terminal plates 22 and 22a. If necessary, a resistance 28 may be interposed between source F and the rectifier, as illustrated.

-This arrangement of connections is illustrated diagrammatically in Fig. 9, from which itwill be seen. that when wire 24 is positive, current flows throughy the-left half of section C,'plate 2,2, batte B, plate 22", section E, and bolt 20 to w1re 25. When wire 25 is positive, current flows .throu h section D, platc'22, battery B, plate and the right half of section C to wire 24.

lVhen the rectifier is required to carry a comparativel large amount of current, a structure suc as that illustrated in Fig. 10 may be employed. In this view, 10 is'the metal plate provided with a layer of oxide 10, 11 is the lead foil, and 12 is the other electrode plate, all as .in Fig. 1, except that these elements 'are of 'considerably greater area andare clamped together by a lurality of spaced bolts 29. Each bolt 1s electrically isolated from the upper plate 12 by 30 of suitable shape.

an insulating bushing Y ead foil 1s 1n sections As here shown, the

' which are located adjacent the bolts, al-

though this foil may be in one strip orsheet, perforated to accommodate the bolts. A number of units similar to the one shown in Fig. 1( may, of course, be assembled and Lacasse connected in the manner shown in Fig. 9 so as` to utilize both halves of each alternating current wave if desired.

Although I have herein -shown and described only'a few formsl of devices embodying my invention, it is understood that vari,- ous changes and modifications may be made therein within the scope of the appended claims without departing from the lspirit and scope of m invention. l

Having thus escribed my invention, what I claim is:

1. In combination, copper having cuprous oxide formed thereon said combination constituting in and of 1tself a uni-directional current car ing device.

2.. Incom ination, copper having cuprous .oxide formed thereon, said combinationconstituting in and of itself a uni-directional current carrying device, and means for making intimate contact with said cuprous oxide to' establish an electric circuit through said combination.

3.. In combination, a metal having an oxide of the metal formed thereon, said combination constituting inand .of itself a unidirectional current carrying device. f

` 4. In combination, a metal havin. an eleci combination constituting in and of itself a uni-'directional current carrying device, finely divided carbon rubbed into the free surface of said compound, and an impressionable electrode pressed into intimate electrlcal contact with said carbon.

7. In combination, a metal having formed thereon a compound which conducts` current electronically, said combination constituting in and of itself a uni-directional current carryingdevice.

8. n combination, a metal and an electroconductive coin ound in intimate and permanent electrica contact'with said metal, said combination constituting in and of itself anni-directional current carrying device, an impressionable. electrode in contact with said compound, and means for pressinfr said electrode against said compound witi considerable force. y

9. A bolt, a lurality of units mounted thereon and eac comprising the combination of a metal with a compound of` the metal formed thereon, such combination con-- stituting in and of itself a uni-directional current carrying device, an im ressionaiile electrode in engagement with t e free sur- `face of the compound in each unit, a .metal washer larger `in diameter than the other elements interposed between each two'units to provide for heat radiation, and a nut for. clamping said units together on said bolt.

l0. In a rcctifyingdevice, a copper meniber constituting the cathode ot' the rectifier,

a layer of cuprous oxide formed on, at least,l

of the rectifier, said two bodies being integrally' united over a relatively extended area, thejunction between said bodies permittingA a relatively free flow of electrons from the copper to the oxide While obstructing electron flow in opposite direction under substantial absence of electrolytic or chemical changes, t-he lthickness and configuration of said bodies on both sides of said junction being such as to protect said junction against external influences tending to impair the permanency of therectifying properties thereof.

12.` In a rectier device, a copper plate constituting the cathode of the rectifier, a solid layer of cuprous oxide integrally formed over a relatively extended portion of the surface of said plate, the junction between said bodies being utilized to permit a relatively free How 'of electrons from the copper to the oxide While obstructing elec-y tron How in opposite direction under substantial absence of electrolytic or chemical changes in the 13. In a rectifier device, a copper p'late constituting the cathode of the rectifier, a layer of cuprous oxide adheringly united to said copper plate over an extended ortion of the surface. thereof and constituting the anode of the rectifier, means for providing a bi-laterally conducting terminal connection with the side of the oxide 4layer opposite the junction with the copper, the junction between the oxide layer and the copper serving to permit a How of current in the direction from said oxide to said copi per while -preventing a flow of current in opposite direction under substantial absence of electrolytic conduction in the portions ndjacent said junction.

14. In a rectifying device, a coppery plate having a vlayer of cuprous oxide. integrally formed over a relatively large portion of the portions near said junction.`

surface -thereof, means for providing a bilateral conducting connection with the side of the oxlde layer opposite its junction with the copper over substantially a large portion .chemical changes adjacent to the rectifying junction.

15. In a rectifying device, two dissimilar. bi-laterally conducting bodiesintegra'lly and permanently joined to each other over an extended area, the junction between said two bodies constituting a uni-directional current valve permitting substantially free electron flow onl in one direction thereacross under substantlal absence of electrolytic or chemical changes in the portions of the two bodies adjacent to said junction.

16. In a rectifying device, two dissimilar bi-laterally conducting bodies integrally joined to each other over an extended area, 'the junction between said two bodies constituting a uni-directional current valve permitting substantially free electron How only in one direction thereacross under substantial absence of electrolytic or chemical changes in the portions of the two bodies adjacent to said junction, the conductivity of one of said bodies being relatively low as compared to the conductivity of the other of said bodies.A

17. In a rectifying device, a solid body of metal having formed thereon an adhering laye-r of a chemically different compound having a substantially higher resistance than said metal, andnieans for utilizing the junction between said metal and said compound'- as a uni-directional current valve permitting lim a substantially free flow of electrons therethrough on'ly in one direction, the thickness of said compound being sufiicient to prevent dislodgment of particles near said junction, and means for establishing a conducting terminal connection lwith an extended area of the side of' said layer opposite its junction with said metal.

18. A rectifying unit comprising a. body consisting of a metal having an electronically conducting compound of the metal formed thereon and integral therewith, the junction between said metal and said compound being 12" permanent and uni-laterally conducting.

19. A recti ing unit comprising a metal a layer of w. ich is transformed into an electronically conducting compound in situ. the compound and ythe metal forming an in- 1T' tegral body and the junction between them being uni-laterally conducting.

20. A body consisting of a metal having an electronically conducting compound of the metal formed thereon and integral there- 13" pressionuble electrode in engagement with the free surface of the compound in each unit, a metal washer larger 1n diameter than the other elemente interposed between cach two units to provide for heut radiation, and a nut for clamping said units together on said bolt.

1n testimony whereof I aliix in signature.

LARS O. GR() DA1-IL.

,DISCLAIMER l,640,335.-Lafrs O. Granda/Ll, Pittsburgh, Pa.

Patent datedAugust 23, 1927.

DEVICE.

UNIDlnno'rIoNAL (EUnnnN'r-(lnnln'iNo Dl'sclalmor iled llebruary 2i), 1932,

by the assignee, Im 4U'n/iofn, Switch and Signal Oompmiy. H'ereby enters the following disclaimer, to wit: 1. Your petitioner hereby dist-,laune the snlnect-mattcr ol claims 3, 4, 5, 7, 9, 15, 16,

17, 18, li), and 20.

2. Your petitioner hereby disclaims the subject-matter oll claime` l and 2, except combinations in which rectification il. Your petitioner hereby disclaims the subject-matter ol` claims takes place over a relatively wide area :it the internal boundary of the copper and cuprous oxlde l'ormed thereon.

(i and 8, except combinations` in which the metal is copper and the compound is cuprous oxide and the rectilication takes place over a relatively wide area at the internal boundary ol the copper and cnprous oxide. formed thereon.

lOiciol Gazette Marc/t 22, 1932.] 

